The present invention relates to a robot arm, more particularly, to a robot arm having a plurality of hydraulic rotary actuators that are controlled by pressurized working fluid.
Hydraulic actuators are smaller and more adapt to precision control in comparison with the more commonly used hydraulic cylinders and have much better output-to-size ratio characteristics than actuators based on electric motors. Rotary motion actuators and linear motion actuators are employed in developing a wide range of robots, such as mobile robots (automatons), wearable robots, heavy duty robot arms and the more recent underwater manipulators that can freely operate in deep sea environments where humans can hardly do so. A rotary actuator with a rotary actuator type joint structure has been disclosed by the same applicant in Korean Patent Application No. 10-2009-0112047.
In order to operate a conventional hydraulic actuator, it was necessary that a pressurized working fluid communicate between the pumping station and the hydraulic actuator through entry and exit lines that were externally exposed in the open.
The externally exposed entry and exit lines of the working fluid may cause problems, such as being very complex to discern and install the numerous lines correctly as well as being limited in motion of the moving structures by the length of the lines. In addition, having the entry and exit lines of the working fluid externally exposed may cause the lines to unintentionally come into contact with the moving structures or other extraneous objects thereby increasing the need for maintenance and repair.